which one will go first overall? Let me hear your thoughts and speculations on who and why?

Depends on who wants what type of player. Hischer is more dynamic like MacKinnon, Patrick is more of the Getzlaf type, he might get 20 goals, but is probably going to use his size to create more space as opposed to his skill. Either would be the number one center in St. Louis. Personally, as a Blues fan I'd rather take Patrick (even though there's no way the Blues can get him in the draft), but it's because I thin he fits in more with the team philosophy. But it's really a toss up to be honest. Assuming the Avs get the number one pick, they might trade down to a different team in the top 10 if they find a need elsewhere and they think they can get a decent return for the 1st overall. They don't need another center with Jost in the pipeline (he should sign after the season) and Compher coming in. Avs need defense and scoring wingers.

If my team (Boston) misses out on the playoffs and were somehow to win the lottery I would totally trade down if I were the real GM. I think 1st overall pick is more valuable then any player in this draft, even though one of the players will be selected and one team may prefer a certain guy so they'll want #1, I just don't see that much difference between the top 5 or so players. If I could trade from #1 to #5 and pick up some help this year, a second round pick (top 40) or a prospect who's worth atleast a second rounder: I'd definitely do it. I really don't see any guy in this draft being a real franchise player, so why not move down if someone will pay you a fair price for the pick. Is Hischier and Patrick really that much better than all of ; Liljegren, Heiskanen, Glass, Vilardi, Rasmussen, Necas, Suzuki, Kostin, Tippet... ect... ect... If I could trade from #1 to #10 and pick up the teams next year first, while still getting one of these guys this year, I think it would make sense. Next year should be a stronger draft and you'd be adding 2 bodies instead of one.

I would like to see the Devils select Nico Hischier, I believe he has more of an offensive upside which the Devils desperately need. I have heard Nolan Patrick described as the perfect #2 center on a good team, which I believe can be found in later rounds of other drafts, and it's not like the Devils have a clear number one center on the roster or in the prospect pool. In my opinion when selecting number one, it is crucial to select a dynamic player. I like Patrick and I think he is the safer choice at #1, but I would like to see the Devils take the risk and select Hischier. Now on the other hand if Philadelphia had the #1 overall selection I believe they would take Patrick, he is a type of player they don't have, he is a big body that would fit in perfectly behind Giroux for the next couple of seasons where he would shine. In my opinion, due to the Devils inability and ineptness inside the offensive zone selecting the more dynamic player is the better choice at #1.

I think Nico Hischier and Pavel Zacha being a 1-2 punch down the middle is fantastic for the Devs. I believe they take Patrick, but to me Hischier is going to be the better player

I think Nico Hischier is the better player and has the higher ceiling as well. There is a lot more natural skill there and he just has more game-breaking potential.

Based on some basic information
Nolan Patrick is a 1.257 points per game in the WHL. 6'3 200 lbs and has been ranked 1 by a lot of scouts. However, he did have the serious injury in his draft year, much like Morgan Reilly who dropped because he was injured.
Nico Hischier is a 1.508 points per game. He's a little smaller at 6'0 180. The question I have is that Hischier's sample size is so much smaller than Patrick's. 86 points in 57 games in the Q is good, I am not taking that away from him, but the sample size is smaller and there are questions if this was just a flash in the pan. We only have this one season of to really look at and judge his skills on North American ice.
With Patrick, we can look at a track record over three years to see that he is improving. In his first full year, he was a 1.018 p/g. In his second year, he was a 1.416 p/g. This year there was a small dip at 1.393 p/g. I think that a GM would be drawn more to a track record than one season.
If we look at some point per game comparable with similar height/weight that go in the upper half of the first round for Hischer a good comparable in point per game is Nathan MacKinnon. A good height/weight comparable is Johnathan Huberdeau. using these comparable we can project that at his prime Hischer will produce around .65-.69 points per game. using Huberdeau as a comparable also accounts for any drops in Hischers point per game Q stats lowering due to a smaller shooting percentage or any regression.
For Patrick, Ryan Johansen fits a height/weight and points per game comparable, for another one (based on if Patrick had not been injured since recovery does take a step out of your game) Leon Draisaitl. We can project Patrick will average about the same point per game as Hischer, though he will not be as flashy.
Here are the pros of both players, they will both reach at least 300 games in the NHL baring any unfortunate injuries. They will both produce at maybe not elite center production but at least a 1b or 2nd line center.
My guess (since it really is a toss up) Patrick will go first based on the track record.